/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.table.planner.calcite;

import org.apache.calcite.rel.type.RelDataTypeFactory;
import org.apache.calcite.rex.RexBuilder;
import org.apache.calcite.rex.RexNode;

/**
 * A slim extension over a {@link RexBuilder}.
 * See the overridden methods for more explanation.
 */
public final class FlinkRexBuilder extends RexBuilder {
	public FlinkRexBuilder(RelDataTypeFactory typeFactory) {
		super(typeFactory);
	}

	/**
	 * Compared to the original method we adjust the nullability of the nested column based on
	 * the nullability of the enclosing type.
	 *
	 * <p>If the fields type is NOT NULL, but the enclosing ROW is nullable we still can produce nulls.
	 */
	@Override
	public RexNode makeFieldAccess(
			RexNode expr,
			String fieldName,
			boolean caseSensitive) {
		RexNode field = super.makeFieldAccess(expr, fieldName, caseSensitive);
		if (expr.getType().isNullable() && !field.getType().isNullable()) {
			return makeCast(typeFactory.createTypeWithNullability(field.getType(), true), field, true);
		}

		return field;
	}

	/**
	 * Compared to the original method we adjust the nullability of the nested column based on
	 * the nullability of the enclosing type.
	 *
	 * <p>If the fields type is NOT NULL, but the enclosing ROW is nullable we still can produce nulls.
	 */
	@Override
	public RexNode makeFieldAccess(RexNode expr, int i) {
		RexNode field = super.makeFieldAccess(expr, i);
		if (expr.getType().isNullable() && !field.getType().isNullable()) {
			return makeCast(typeFactory.createTypeWithNullability(field.getType(), true), field, true);
		}

		return field;
	}
}
